Shelf



FIG. 1 is a front perspective front view of a shelf showing my new design;

FIG. 2 is a front elevation view thereof;

FIG. 3 is a left side elevation view thereof;

FIG. 4 is a right side elevation view thereof;

FIG. 5 is a top plan view thereof; and,

FIG. 6 is a front perspective view of the shelf in use, wherein the shelf has been opened.

Broken lines are used to illustrate features of the shelf which form no part of the claimed subject matter. 

CLAIM The ornamental design for a shelf, as shown and described. 